package sqlSession;

import pojo.Configuration;
import pojo.MappedStatement;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Proxy;
import java.lang.reflect.Type;
import java.util.List;

public class DefaultSqlSession implements SqlSession {
    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);
        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> list = selectList(statementid, params);
        if (list.size() == 1) {
            return (T) list.get(0);
        } else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }
    }

    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回
        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, (proxy, method, args) -> {

            // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
            // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
            // 方法名：findAll

            String methodName = method.getName();
            String className = method.getDeclaringClass().getName();

            String statementId = className + "." + methodName;



            if (methodName.contains("update")){
                System.out.println("更新方法");
                return this.updateById(statementId,args);
            }

            if (methodName.contains("delete")){
                return this.deleteByCondition(statementId,args);
            }

            if (methodName.contains("add")){
                return this.insert(statementId,args);
            }

            // 准备参数2：params:args
            // 获取被调用方法的返回值类型
            Type genericReturnType = method.getGenericReturnType();
            // 判断是否进行了 泛型类型参数化
            if (genericReturnType instanceof ParameterizedType) {
                List<Object> objects = selectList(statementId, args);
                return objects;
            }
            return selectOne(statementId, args);
        });


        return (T) proxyInstance;
    }

    @Override
    public Integer updateById(String statementid, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
       Integer i = simpleExecutor.update(configuration, mappedStatement, params);
        return i;
    }

    @Override
    public Integer deleteById(String statementid, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        Integer i = simpleExecutor.update(configuration, mappedStatement, params);
        return i;
    }

    @Override
    public Integer deleteByCondition(String statementId, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Integer i = simpleExecutor.delete(configuration, mappedStatement, params);
        return i;
    }

    @Override
    public Integer insert(String statementId, Object... params) throws Exception {
        //将要去完成对simpleExecutor里的query方法的调用
        SimpleExecutor simpleExecutor = new SimpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        Integer i = simpleExecutor.insert(configuration, mappedStatement, params);
        return i;
    }
}
